Dark-matter decays and self-gravitating halos
We consider models in which a dark-matter particle decays to a slightly less massive daughter particle and a noninteracting massless particle. The decay gives the daughter particle a small velocity kick. Self-gravitating dark-matter halos that have a virial velocity smaller than this velocity kick may be disrupted by these particle decays, while those with larger virial velocities will be heated. We use numerical simulations to follow the detailed evolution of the total mass and density profile of self-gravitating systems composed of particles that undergo such velocity kicks as a function of the kick speed (relative to the virial velocity) and the decay time (relative to the dynamical time). We show how these decays will affect the halo mass-concentration relation and mass function. Using measurements of the halo mass-concentration relation and galaxy-cluster mass function to constrain the lifetime–kick-velocity parameter space for decaying dark matter, we find roughly that the observations rule out the combination of kick velocities greater than 100 km s^(-1) and decay times less than a few times the age of the Universe.
Additional Information© 2010 The American Physical Society. Received 1 March 2010; published 3 May 2010. We thank Andrew Benson for helpful discussions. This work was supported at Caltech by DOE Grant No. DEFG03-92-ER40701 and the Gordon and Betty Moore Foundation.
Published - Peter2010p10418Phys_Rev_D.pdf